Not Applicable
Electronic equipment often employs a circuit board or interconnection panel such as a backplane, and to which one or more circuit boards, often called daughter boards, are connected. The daughter boards are disposed perpendicular to the backplane and are connected thereto by mating connectors. The connector on the daughter board is typically an edge card connector which is disposed along one edge of the board and which provides electrical interconnection from contact pads on a surface of the board to connector contacts in the edge card connector. This connector is mateable to a complementary connector mounted on the backplane. The edge card connectors are separately manufactured components which add to the cost and bulk of a board assembly. For many purposes the distance between an array of daughter boards which may be mounted on a backplane is limited by the physical size of the connectors. As electronic devices operate at ever increasing frequencies, it becomes increasingly important to minimize the length of interconnecting paths on circuit boards containing the electronic components and in electronic assemblies composed of interconnected boards. The use of board connectors adds to the electrical path length and can thereby limit the speed of the board assembly.
In conventional printed circuit boards conductive traces are provided on one or more layers of insulating material and conductive traces of inner layers are interconnected to the conductive traces of other inner layers or surface layers by conductive vias which extend between layers at selected positions. Selected traces are connected to a pad or plated hole located on the top and/or bottom of the circuit board and connectors are attached along the edge of the board and mated to the corresponding pads or holes. Signals must travel along the traces in the circuit board and travel outside the circuit board through the mating connectors.
The edge card connectors can be of the saddle mount type in which a connector body has a slot into which an edge of the circuit board is disposed, or of the right angled type in which the connector body is mounted to a surface of the board near an edge of the circuit board. The electrical path lengths of these conventional board interconnection arrangements are increased by the interconnection paths through the connectors.
In the present invention the circuit traces of a circuit board extend to and usually outward from a side surface of the board for direct connection to contacts of a mating connector, circuit board or device. The traces can also extend to multiple side surfaces of the circuit board. The contact portions of the traces are the end surfaces of the traces which in one embodiment extend outward of the plane of the associated side surface of the circuit board. Alternatively the traces may extend to a plane inward of the plane of the associated side surface of the circuit board or to the plane of the side surface. The contact portion may be of greater cross-sectional area than that of the associated trace to provide a contact area of intended size. The contact portion of a trace may be plated with gold or other appropriate conductive material to enhance conductivity and prevent or minimize oxidation or corrosion. Contact pads may be deposited on or attached to the contact ends of the traces.
Interconnection to the contact portions of the traces is provided by mating contacts which respectively engage the contact end surfaces of the traces. Preferably, the mating contacts are resilient conductive columns or elements which are maintained in engagement with the contact ends by suitable hardware.
The speed of a circuit board constructed in accordance with the invention is improved since signal path lengths can be minimized by the in-line interconnection of board traces to a mating circuit board or device. Spacing between adjacent boards can also be reduced by the absence of bulky connectors. The absence of board connectors also permits high I/O xe2x80x9cpin countsxe2x80x9d since the contact portions of the traces can be more closely spaced than conventional contact pads.